1. Field of the Invention
The present invention relates to a disk drive for handling a disk-shaped record medium such as a magneto-optic disk, and a method for processing data using the same. Specifically, the present invention relates to an optical disk drive structured in such a manner that a reference clock having a frequency corresponding to a reproduction frequency of data reproduced from a data recording region is divided in accordance with a ratio between a record density of a header region where pre-formatted data including a sector mark for indicating a leading position of a sector is recorded, and a recording density of a data recording region subsequent to the header region, so as to produce a sampling clock, and by use of thus-produced sampling clock, the sector mark is detected. This structure enables, even if the header region has a recording density different from the recording density of the data region, to use a sector mark detector having the same structure as of a sector mark detector which is employed in the case where the header region has the same recording density as that of the data region and therefore a reference clock is used, thereby producing the optical disk drive at a low cost.
2. Description of the Related Art
FIG. 1 is a diagram showing a sector format of a magneto-optic disk (ISO/IEC 15286) of 5.2 GB on each of its sides. The numbers in FIG. 1 indicate numbers of bytes.
One sector is divided into a header, a transition area TA1, an ALPC gap, a VFO3, a sync-field, a data field, a postamble PA2, a buffer field, and a transition area TA2 in order of recording/reproduction.
This sector is broadly constituted by an address section (i.e. a header) and a data section. At the front and back of the data section, the ALPC gap, the transition area TA1, and the TA2 are placed. The header is a region exclusively used for reproduction, and in the header, so-called emboss pit are pre-formatted and recorded. The area other than the header, that is, the area from the transition area TA1 to the transition area TA2 is a magneto-optic (MO) area.
The header of 64 bytes as the address section is constituted by a sector mark SM (8 bytes), VFO1 in the VFO field (26 bytes), an address mark AM1 (1 byte), ID1 in the ID field (5 bytes), VFO2 in the VFO field (16 bytes), an address mark AM2 (1 byte), ID2 in the ID field (5 bytes), and postamble PA1 (2 bytes) in this order.
The sector mark SM is a mark used for identifying the initiation of the sector. The sector mark SM has a pattern which is formed by embossing and will not occur by (1-7) RLL code or (2-7) RLL code.
The VFO field is used to synchronize the variable frequency oscillator (VFO) at a phase-locked loop (PLL) section in the disk drive. In other words, the VFO field is a field into which the phase-locked loop is retracted. The VFO field in one sector is constituted by VFO1, VFO2, and VFO3. In the address section, VFO1 and VFO2 are formed by embossing. VFO3 is provided in the data section, and when data is recorded in the sector, the data is magneto-optically recorded in the VFO3.
In VFO1 and VFO2, recorded is a signal with a predetermined pattern for retracting the phase-locked loop (i.e. for generating a read clock) to read the data from the header. On the other hand, in VFO3, recorded is a signal with a predetermined pattern for retracting the phase-locked loop (i.e. for generating a read clock) to read the data from the data section.
The address marks AM1, AM2 are used for synchronization of bytes for the subsequent ID field, and have predetermined patterns. In the address section, the address marks AM1, AM2 are formed by embossing. The ID field is constituted by sector address information, that is, information about track number and sector number (3 bytes), and CRC byte (2 bytes) for detecting error which has occurred in the track number and sector number information in this order. Into the ID fields ID1, ID2, each having 5 bytes, the same data is recorded. In the address section, ID1 and ID2 are formed by embossing.
Subsequent to the header, an ALPC gap is placed via the transition area TA1. The ALPC gap is used for obtaining time that the disk drive needs for the processing performed after the reading from the header is completed, for permitting the displacement of the position of the subsequent VFO3, for testing laser power at the time of recording, and the like.
The data section is constituted by VFO3, a sync-field, a data field, postamble PA2, and a buffer field. The sync-field is used for synchronization of bytes for the data field subsequent to the sync-field, and has a predetermined bit pattern.
The data field is provided for recording user data. In the data field, 2048 bytes are reserved for the user data. In addition to the user data, parities, and the like for error detection and error correction are also recorded in the data field. As a result, the data field has 2498 bytes. The buffer field is a margin for rotation jitter.
FIG. 2 is a diagram showing a data structure of a magneto-optic disk having 2048 byte/sector.
xe2x80x9cSB1xe2x80x9d to xe2x80x9cSB4xe2x80x9d are sync bytes, and are synchronization signals which are recorded in the sync-field described above. xe2x80x9cRS1xe2x80x9d to xe2x80x9cRS59xe2x80x9d are resync bytes for resynchronization, and are provided at every 40 bytes, that is, at every 2 interleaves. xe2x80x9cD1xe2x80x9d to xe2x80x9cD2048xe2x80x9d are user bytes, and are provided into a length of 20 bytes in a column direction and sequentially in a row direction. xe2x80x9cSWF1xe2x80x9d and xe2x80x9cSWF2xe2x80x9d are sector written flag (SWF) bytes. xe2x80x9cC1xe2x80x9d to xe2x80x9cC4xe2x80x9d are CRC bytes. xe2x80x9cE1, 1xe2x80x9d to xe2x80x9cE20, 16xe2x80x9d are parities for error correction. The parities are generated in a row direction.
In the magneto-optic disk of 5.2 GB on each of its sides, the header (i.e. the address section) and the data section have the same recording densities with each other. Hereinafter, the process of reading data from this magneto-optic disk will be briefly described.
First, a sector mark is detected from the reproduction data by use of a reference clock having a frequency which corresponds to the reproduction frequency of the data to be reproduced from the data section. As a result of detecting the sector mark, it is acknowledged that there is an ID field located in a rearward position. Then, an address mark AM1 is detected from the reproduction data by use of the read clock obtained by retracting phase-locked loop into VFO1. In this case, in order to prevent erroneous detection, a detection window for address mark is created. The detection of address mark is permitted only during the period when the window is opened. The detection window is created based on a count value obtained by counting the reference clock based on the position where the sector mark is detected.
When the address mark AM1 is detected, the ID field ID1 of 5 bytes subsequent to the address mark AM 1 is read and decoded to obtain sector address information (i.e. information about track number and sector number). From the sector address information, the current position is acknowledged. The same process is performed in the subsequent VFO2, AM2, and ID2. If it is impossible to read ID1, the current position is acknowledged in ID2. As a result of acknowledging the current position, if the sector is a target sector, the reading from the data field is performed. At this time, the data field is different from the ID field only in that the data field has sync bytes and resync bytes, instead of address mark.
In recent years, as one of techniques for giving higher density to magneto-optic disks, a magnetically induced super resolution (MSR) reproduction method has been suggested. The MSR reproduction method is a technique capable of reading recorded information from a region having an area smaller than a laser beam spot, by use of magnetic films having different temperature characteristics from each other. It is possible, therefore, to read information recorded in high density from MSR media with no need of reducing the diameter of laser beam spot, if the MSR media have a recording region with two-layered structure constituted by two magnetic films having different temperature characteristics.
The MSR reproduction method will be described in more detail. FIG. 3A is a diagram showing a recording track Dt and a spot Bs of a laser beam irradiated onto the recording track Dt. FIG. 3B is a diagram partially showing a cross-section of a magneto-optic disk. In order to achieve the effect of MSR, as shown in FIG. 3B, the magneto-optic disk is required to have a recording layer and reproduction layer which exhibit different magnetic characteristics from each other according to temperature.
The reproduction layer is a mask Ms for shielding the recording layer from the spot Bs of the laser beam Lb. As seen in FIGS. 3A and 3B, when a laser beam Lb with laser power at a level of reproduction is irradiated onto the reproduction layer, a small window (i.e. an aperture Ap) is formed on the reproduction layer. The direction of magnetization mt of the recording bit Rb of the recording layer, which is located beneath the aperture Ap, is transferred. By observing the direction of magnetization mt which has been transferred to the reproduction layer, the recording bit Rb recorded in high density can be read, even if the laser beam Lb has a large spot diameter.
As describe above, the direction of magnetization mt is transferred from the recording layer to the reproduction layer by irradiation of the laser beam Lb with laser power at a level of reproduction. At this time, it is possible to control the size of aperture Ap, that is, the area where the direction of magnetization is transferred from the recording layer to the reproduction layer by adjusting the laser power at a level of reproduction of the laser beam. Therefore, it is possible to exploit the frequency characteristics of the signal reproduced from the magneto-optic disk by successfully controlling the level of laser power for reproduction. The use of MSR reproduction technique such as described above makes it possible to reproduce data recorded in a density two times or higher than the case where no MSR technique is used, even if a beam with the same spot diameter is used.
As described above, the use of MSR reproduction technique greatly increases the recording capacity of the magneto-optic disk. However, the MSR reproduction technique is not applicable to the entire area of the magneto-optic disk. As has been described above, the magneto-optic disk employs a recording unit referred to as a sector, as a basic data format on the disk. The sector is formed by a header in which pre-formatted data is recorded by emboss pits, and an MO area where data can be recorded and reproduced (i.e. a data recording region). In thus-structured magneto-optic disk, a recording film intended for use in MSR reproduction method can be formed in the MO area. In the header, it is impossible to perform the MSR reproduction method.
As described above, it is impossible to perform the MSR reproduction method in the header. Therefore, the MSR reproduction method is performed in the MO area. In the magneto-optic disk where the MSR reproduction method is performed in its MO area, in order to stably read data from its header, the recording density in the header is inevitably suppressed to be lower than the recording density in the MO area. In this case, it is impossible to use the sector mark detector as it is which uses a reference clock with a frequency corresponding to the reproduction frequency of the data reproduced from the data section. This is because, as has been described above, the reference clock does not correspond to the reproduction frequency of the data reproduced from the header.
The objective of the present invention is to provide an optical disk drive capable of using, even if the header region has a recording density different from that of the data recording region, a sector mark detector having the same structure as that used in the case where the header region and the data recording region have the same recording densities, and therefore the reference clock is used.
In an aspect of the present invention, an optical disk drive for handling an optical disk in which a sector as a recording unit is formed by a header region where pre-formatted data including a sector mark for indicating a leading position of a sector and a data recording region subsequent to the header region, and the header region has a recording density different from the recording density of the data recording region, includes: a data reproduction device for reproducing the pre-formatted data from the header region in the sector, and for reproducing data from the data recording region of the sector; a clock generator for generating a reference clock with a frequency corresponding to a reproduction frequency of the data reproduced from the data recording region in the sector; a divider for dividing the reference clock in accordance with the ratio between the recording density of the header region and the recording density of the data recording region, so as to generate a sampling clock with a frequency corresponding to the reproduction frequency of the pre-formatted data reproduced from the header region; and a sector mark detector for detecting the sector mark from the pre-formatted data reproduced in the data reproducing device, by use of the sampling clock.
In another aspect of the present invention, a method for processing reproduction data in an optical disk drive for handling an optical disk in which a sector as a recording unit is formed by a header region where pre-formatted data including a sector mark for indicating a leading position of a sector and a data recording region subsequent to the header region, and the header region has a recording density different from the recording density of the data recording region, includes the steps of: reproducing the pre-formatted data from the header region in the sector, and for reproducing data from the data recording region of the sector; generating a reference clock with a frequency corresponding to a reproduction frequency of the data reproduced from the data recording region in the sector; dividing the reference clock in accordance with the ratio between the recording density of the header region and the recording density of the data recording region, so as to generate a sampling clock with a frequency corresponding to the reproduction frequency of the pre-formatted data reproduced from the header region; and detecting the sector mark from the pre-formatted data reproduced in the data reproducing device, by use of the sampling clock.
In the present invention, handled is an optical disk in which a sector as a recording unit is formed by a header region and a data recording region, and the header region has a recording density different from the recording density of the data recording region. For example, the ratio between the recording density of the header region and the recording density of the data recording region is 1/2. Pre-formatted data is reproduced from the header region in the sector, and data is reproduced from the data recording region in the sector.
Then, a reference clock with a frequency corresponding to the reproduction frequency of the data reproduced from the data recording region in the sector is produced. For example, in the case of employing a zone constant angular velocity (ZCAV) method, the optical disk has a recording region divided into plural zones in its radial direction. The reference clock frequency produced by the clock generator has a frequency different from zone to zone.
The reference clock is divided in accordance with the ratio between the recording density of the header region and the recording density of the data recording region. Then, a sampling clock with a frequency corresponding to the reproduction frequency of the pre-formatted data reproduced from the header region is produced. By use of thus-produced sampling clock, a sector mark is detected from the pre-formatted data.
As described above, the sampling clock is produced by dividing the reference clock, and the sector mark is detected by use of thus-produced sampling clock. With this arrangement, even if the header region has a recording density different from the recording density of the data recording region, it is possible to use a sector-mark detector having the same structure as of a sector mark detector used in the case where the header region and the data recording region have the same recording densities, and therefore a reference clock is used. The optical disk drive with this structure can be obtained at a low cost.
In addition, a window signal for designating the range in which the address mark is to be detected from the pre-formatted data is produced by use of the aforementioned sampling clock. With this arrangement, even if the header region has a recording density different from the recording density of the data recording region, it is possible to use a window generator having the same structure as of a window generator used in the case where the header region and the data recording region have the same recording densities, and therefore a reference clock is used. The optical disk drive with this structure can be obtained at a low cost.
In still another aspect of the present invention, an optical disk drive for handling an optical disk in which a sector as a recording unit is formed by a header region and a data recording region subsequent to the header region, includes: an information obtaining device for obtaining information about a ratio between the recording density of the header region and the recording density of the data recording density; a data reproduction device for reproducing the pre-formatted data from the header region in the sector, and for reproducing data from the data recording region of the sector; a clock generator for generating a reference clock with a frequency corresponding to a reproduction frequency of the data reproduced from the data recording region in the sector; a divider for dividing the reference clock in accordance with the ratio between the recording density of the header region and the recording density of the data recording region, so as to generate a sampling clock with a frequency corresponding to the reproduction frequency of the pre-formatted data reproduced from the header region; and a sector mark detector for detecting the sector mark from the pre-formatted data reproduced in the data reproducing device, by use of the sampling clock.
In still another aspect of the present invention, a method for processing data in an optical disk drive for handling an optical disk in which a sector as a recording unit is formed by a header region and a data recording region subsequent to the header region, includes the steps of: obtaining information about a ratio between the recording density of the header region and the recording density of the data recording density; reproducing the pre-formatted data from the header region in the sector, and for reproducing data from the data recording region of the sector; generating a reference clock with a frequency corresponding to a reproduction frequency of the data reproduced from the data recording region in the sector; dividing the reference clock in accordance with the ratio between the recording density of the header region and the recording density of the data recording region, so as to generate a sampling clock with a frequency corresponding to the reproduction frequency of the pre-formatted data reproduced from the header region; and detecting the sector mark from the pre-formatted data reproduced in the data reproducing device, by use of the sampling clock.
In the present invention, handled are various kinds of optical disks each in which a sector as a recording unit is formed by a header region and a data recording region, and the header region has a recording density different from the recording density of the data recording region. For example, the ratio between the recording density of the header region and the recording density of the data recording region is 1, 1/2, and the like. When an optical disk is mounted onto the optical disk drive, information about the ratio of the recording density of the header region and the recording density of the data recording region is obtained. This information is obtained by, for example, being reproduced from an information recording region that the optical disk has.
Pre-formatted data is reproduced from the header region in the sector, and data is reproduced from the data recording region in the sector of the optical disk mounted onto the optical disk drive. For example, in the case of employing a zone constant angular velocity (ZCAV) method, the optical disk has a recording region divided into plural zones in its radius direction. The reference clock produced by the clock generator has a frequency different from zone to zone.
The reference clock is divided in accordance with the ratio, obtained in the above-described manner, between the recording density of the header region and the recording density of the data recording region, so as to produce a sampling clock with a frequency corresponding to the reproduction frequency of the pre-formatted data reproduced from the header region. By use of thus-produced sampling clock, a sector mark is detected from the pre-formatted data.
As described above, the sampling clock is produced by dividing the reference clock, and the sector mark is detected by use of thus-produced sampling clock. With this arrangement, even in the case of handing an optical disk in which the header region has a recording density different from the recording density of the data recording region, it is possible to use a sector mark detector having the same structure as of a sector mark detector used in the case where the header region and the data recording region have the same recording densities, and therefore a reference clock is used. The optical disk drive with this structure can be obtained at a low cost.
In addition, a window signal for designating the range in which the address mark is to be detected from the pre-formatted data is produced by use of the aforementioned sampling clock. With this arrangement, even in the case of handling an optical disk in which the header region has a recording density different from the recording density of the data recording region, it is possible to use a window generator having the same structure as of a window generator used in the case where the header region and the data recording region have the same recording densities, and therefore a reference clock is used. The optical disk drive with this structure can be obtained at a low cost.
The information about the ratio between the recording density of the header region and the recording density of the data recording region is obtained, for example, from the optical disk mounted to the optical disk drive, and the dividing ratio is automatically switched. With this structure, even if various kinds of optical disks having various ratio between the recording density of the header region and the recording density of the data recording region are mounted, it is possible to use sector mark detectors of the same structure and window generators of the same structure for these optical disks. The optical disk drive with this structure can be obtained at a low cost. In addition, since the dividing ratio is not manually switched, the user can omit the procedure of switching the dividing ratio.